Impact of Cotton Production Systems on Management of Hoplolaimus columbus

The effectiveness of selected cultural practices in managing the Columbia lance nematode, Hoplolaimus columbus, on cotton was evaluated in experiments in growers'' infested fields. The effects of planting date, cotton cultivar, treatment with the growth regulator mepiquat chloride, and destruction of cotton-root systems after harvest on cotton-lint yield and population densities of H. columbus were studied. The yield of cotton cultivar Deltapine 50 was negatively related (P = 0.054) to initial population density of H. columbus whereas the yield of Deltapine 90 was not affected by preplant density of this nematode, indicating tolerance in Deltapine 90. Reproduction of this nematode did not differ on the two cultivars. Planting date and treatment with the growth regulator mepiquat chloride did not influence cotton yield in a consistent manner. Application of mepiquat chloride suppressed (P ≤ 0.05) numbers of Columbia lance nematode, although there was an interaction (P ≤ 0.05) with cultivar and year. Early vs. late destruction of cotton-root systems did not impact population densities of this nematode either year, and had no impact on the subsequent cotton crop. The nematicide fenamiphos increased (P ≤ 0.03) cotton yield when H. columbus numbers exceeded the damage threshold.     

Interaction between Meloidogyne incognita and Hoplolaimus columbus on Davis Soybean

Greenhouse and laboratory experiments were performed to determine if an interaction exists between Meloidogyne incognita and Hoplolaimus columbus on Davis soybean. Greenhouse tests were performed with three population levels of M. incognita and H. columbus (0, 1,500, 6,000/1.5-liter pot) separately and in all combinations. Dry root weight (DRT) declined nonlinearly and dry shoot weight (DST) declined linearly with respect to increasing initial populations of M. incognita and H. columbus. When the two nematode species were added to the soil together, the amount of DRT and DST suppression by one species was dependent on the initial level of the concomitant species. The final root population of M. incognita or H. columbus declined linearly with increasing initial population density of the concomitant species. H. columbus suppressed M. incognita populations in the soil nonlinearly, but M. incognita had no effect on H. columbus.     

Pathogenicity and Reproduction of Hoplolaimus columbus and Meloidogyne incognita on 'Davis' Soybean

The effects of initial populations of Hoplolaimus columbus and Meloidogyne incognita on growth and yield of Davis soybean were determined for 1980 and 1981 in microplots and H. columbus in field tests in 1981. M. incognita suppressed yield in microplots both years and H. columbus in 1980. Maximum suppression of dry pod weight by M. incognita was 45% and by H. columbus 35%. The relationship of yield vs. nematode population at planting time was described by a declining exponential model. Maximum reproductive rates for M. incognita and H. columbus were 67.0 and 4.7, respectively, and were inversely proportional to initial population level. Nematode reproductive rates, survival ability, and feeding habits suggest species specific life strategies in the ecological community.     

Dynamics of Concomitant Populations of Hoplolaimus columbus,Scutellonema brachyurum,and Meloidogyne incognita on Cotton

Cotton seedlings grown in a greenhouse and a growth chamber were inoculated with Scutellonema brachyurum, Hoplolaimus columbus, and Meloidogyne incognita, singly and in all possible combinations, at two initial population (Pi) levels (100 and 300/100 cm³). S. brachyurum alone was not pathogenic to cotton at these population levels. It fed primarily as an ectoparasite but matured and reproduced within the root when it penetrated. Populations of S. brachyurum increased in the presence of H. columbus but were suppressed by M. incognita. H. columbus suppressed dry shoot weights of cotton (P = 0.05) at a Pi of 300/100 cm³ soil. Simultaneous inoculation of H. columbus with either M. incognita or S. brachyurum increased H. columbus populations over treatments with H. columbus alone, both at 60 and 90 d after inoculation. M. incognita suppressed cotton shoot weights significantly (P = 0.05) at both Pi levels. Inoculation with S. brachyurum increased M. incognita populations 60 d after inoculation, while H. columbus suppressed populations of M. incognita. Most larvae of M. incognita did not develop to maturity in the presence of H. columbus. Giant cells aborted and were necrotic 20-25 d after inoculation. Since M. incognita and H. columbus feed on different tissues, the inhibition of M. incognita may have resulted from a physiological effect of H. columbus on the host.     

Maximizing the Potential of Cropping Systems for Nematode Management

Quantitative techniques were used to analyze and determine optimal potential profitability of 3-year rotations of cotton, Gossypium hirsutum cv. Coker 315, and soybean, Glycine max cv. Centennial, with increasing population densities of Hoplolaimus columbus. Data collected from naturally infested on-farm research plots were combined with economic information to construct a microcomputer spreadsheet analysis of the cropping system. Nonlinear mathematical functions were fitted to field data to represent damage functions and population dynamic curves. Maximum yield losses due to H. columbus were estimated to be 20% on cotton and 42% on soybean. Maximum at-harvest population densities were calculated to be 182/100 cm³ soil for cotton and 149/100 cm³ soil for soybean. Projected net incomes ranged from a $17.74/ha net loss for the soybean-cotton-soybean sequence to a net profit of $46.80/ha for the cotton-soybean-cotton sequence. The relative profitability of various rotations changed as nematode densities increased, indicating economic thresholds for recommending alternative crop sequences. The utility and power of quantitative optimization was demonstrated for comparisons of rotations under different economic assumptions and with other management alternatives.     

Dynamics of Concomitant Field Populations of Hoplolaimus columbus and Meloidogyne incognita

From the fall of 1968 through the summer of 1973, a Georgia cotton field with a lengthy history of the Cotton Stunt Disease Complex was sampled for the presence of plant parasitic nematodes. Although Meloidogyne incognita was recovered on all sampling dates, concomitant populations of Hoplolaimus columbus were not recovered until the spring of 1970. During the succeeding four growing seasons, the population density and horizontal distribution of H. columbus increased, and H. columbus replaced M. incognita as the predominant phytopathogenie species. A second Georgia cotton field containing concomitant populations of H. columbus and M. incognita was observed from the fall of 1971 through the summer of 1973. In this case the horizontal distribution of both species remained relatively constant and the population density of H. columbus increased steadily. In both locations, the presence of either H. columbus or M. incognita significantly inhibited the presence of the concomitant species. In general, however, the initial spring or final fall population densities of H. columbus or M. incognita had no significant influence on the population density of the concomitant species, The data are also discussed in relation to the biological significance of H. columbus in the southeastern coastal plain.     

Tolerance to Hololaimus columbus in Glyphosate-Resistant,Transgenic Soybean Cultivars

Transgenic soybean cultivars, resistant to glyphosate herbicide in maturity groups V and VI, were evaluated for tolerance to the Columbia lance nematode, Hoplolaimus columbus, in field experiments conducted in 1998 and 1999. Treatment with 43 liter/ha of 1,3-dichloropropene was effective in suppressing H. columbus population densities in a split-plot design. Fumigation increased soybean yield, but a significant cultivar × fumigation interaction indicated variation in cultivar response to H. columbus. A tolerance index (yield of nontreated ÷ yield of treated × 100) was used to compare cultivar differences. Two cultivars in maturity group VI and one cultivar in maturity group V had a tolerance index greater than 90, indicating a high level of tolerance.     

Influence of Poultry Litter Applications on Nematode Communities in Cotton Agroecosystems

The effects of the application of poultry litter at 0.0, 6.7, 13.4, and 20.1 tons/ha on population changes during the growing season on nematode communities were evaluated in two cotton production fields in North Carolina. Numbers of bactivorous nematodes increased at midseason in response to the rate at which litter was applied but decreased with increasing litter application rates at cotton harvest. Numbers of fungivores at cotton harvest were related positively to the rate of litter applied, and this affected a positive increase in the fungivore-to-bacterivore ratio at this sampling date. The rate at which poultry litter was applied resulted in an increase in the bacterivore to plant-parasite ratio, and this corresponded with increased cotton lint yield. Trophic diversity was increased by litter application rate at cotton harvest at one location but not at another. The plant-parasite maturity index was greater consistently at one site than at a second site where the Hoplolaimus columbus population density was above the damage threshold for cotton. The population density of H. columbus was suppressed with increasing rates of poultry litter application, but other plant-parasitic nematodes were affected marginally.     

Effect of Planting Date on Population Densities of Hoplolaimus columbus and Yield of Soybean

During the 1991 and 1992 soybean growing seasons, field plots were established in South Carolina to study the effect of planting date on at-planting nematode densities and subsequent yield losses caused by Hoplolaimus columbus. The susceptible and intolerant soybean cv. Braxton was planted on five dates from to May to 28 June in 1991 and from 12 May to 28 June in 1992. Nematodes were recovered from soil samples collected before nematicide treatment with 1,3-D (Pi), at 6 weeks after planting (Pm), and at harvest (Pf). Initial nematode population densities did not differ among the five dates of planting in either year. The increase in numbers of nematodes from planting to 6 weeks after planting (Pm/Pi) and from planting to harvest (Pf/Pi) were not different among the five planting dates in either year. Root samples also were collected at 6 weeks after planting and at harvest, but planting date did not affect the number of nematodes extracted from roots on any sample date in either year. Altering planting dates between early May and late June was not effective in preventing yield suppression due to H. columbus.     

Damage Functions and Population Changes of Hoplolaimus columbus on Cotton and Soybean

Damage functions and reproductive curves were determined for Hoplolaimus columbus on cotton cv. Deltapine 90 and soybean cv. Gordon over 2 years in field plots in Georgia. Maximum potential yield suppressions of 18% on cotton and 48% on soybean were predicted with respect to increasing Pi. Similar functions indicated yield suppressions of 38% on cotton and 30% on soybean with respect to increasing midseason nematode densities (Pm). Maximum Pf predicted by reproductive curves were 123 and 474/100 cm³ soil on cotton and soybean, respectively. Thresholds at which 10% yield suppression would occur were lower on soybean (Pi of 4) than on cotton (Pi of 70/100 cm³ soil). The economic threshold for a control measure costing $72/ha was a Pi of 60/100 cm³ soil on cotton, assuming a price for cotton lint of $1.44/kg ($0.60/lb), whereas a similar treatment would not be economically feasible on soybean at any Pi with an assumed price of $0.04/kg ($5.50/bu) soybean seed. Damage functions and reproductive curves as determined in this study offer potentially useful tools for analyzing cropping systems and providing decision tools for nematode management.     

A Description of Males of Hoplolaimus columbus

The male of the Columbia lance nematode, Hoplolaimus columbus, is described and illustrated from a harvested soybean field in Holly Hill, South Carolina. It is morphologically similar to the female, except for reproductive structures.     

Crop Rotation and Herbicide Effects on Population Densities of Plant-Parasitic Nematodes

The influence of herbicides and mono- and multicropping sequences on population densities of nematode species common in corn, cotton, peanut, and soybean fields in the southeastern United States was studied for 4 years. Each experimental plot was sampled at monthly intervals. The application of herbicides did not significantly affect nematode population densities. Meloidogyne incognita and Trichodorus christiei increased rapidly on corn and cotton, but were suppressed by peanut and soybean. More Pratylenchus spp. occurred on corn and soybean than on cotton and peanut. Criconemoides ornatus increased rapidly on corn and peanut, but was suppressed by cotton and soybean. Helicotylenchus dihystera was more numerous on cotton and soybean than on corn and peanut. Numbers of Xiphinema americanum remained low on all crops. The peanut sequence was the most effective monocrop system for suppressing most nematode species. Multi-crop systems, corn-peanut-cotton-soybean and cotton-soybean-corn-peanut, were equally effective in suppressing nematode densities.     

Effects of Nematicide Placement on Nematode Populations and Soybean Yields

Four methods of placement of DBCP (l,2-dibromo-3-chloropropane) and a single method of application of ethoprop (0-ethyl S,S-dipropyl phosphorodithioate) wexe compared in each of two areas for control of nematodes on soybeans. One area was a Marlboro sand infested with Hoplolaimus columbus. The other area was a Fuquay loamy sand infested with Meloidogne incognita. Soybean yields were increased and numbers of H. columbus in the row 0-20 cm deep were decreased similarly by all methods of DBCP application in Marlboro soil. All DBCP treatments increased the average soybean yields and decreased numbers of M. incognita larvae in the row 0-20 cm deep in the Fuquay soil. Average root-knot indices were reduced by all DBCP treatments except with placement 40 cm deep beneath the row. Similarly, placement of all or part of the DBCP 20 cm deep and 13 cm to either side of the row resulted in greater average yields than placement of the DBCP 40 cm deep. Apparently, control of M. incognita is more critical 0-20 cm deep than 20-40 cm deep for increasing soybean yields. DBCP did not control H. columbus as effectively as it did M. incognita. Control of H. columbus and M. incognita was not obtained at 0-20-cm and 20-40-cm depths 30 cm and 45 cm from the row regardless of the method used to apply DBCP. H. columbus and M. incognita were controlled more effectively and soybean yields were higher with DBCP at 13.6 kg a.i./ha than with ethoprop at 4.5 kg a.i./ha.     

Seasonal Population Dynamics of Selected Plant-Parasitic Nematodes on Four Monocultured Crops

Seasonal fluctuations in field populations of Meloidogyne incognita, Pratylenchus zeae, P. brachyurus, Criconemoides ornatus, Trichodorus christiei, and Helicotylenchus dihystera on monocultured corn, cotton, peanut, and soybean were determined monthly for 4 yr. Population densities of M. incognita were greater in corn and cotton plots than in peanut and soybean plots from July until January. Those of Pratylenchus spp. were greater on corn and soybean than on cotton and peanut during all months except May and June. C. ornatus populations were greater on corn and peanut than on cotton and soybean during all months. C. ornatus on corn and peanut was more numerous in July than in other months. There was no significant increase in populations of T. christiei, except on corn in June. H. dihystera was greater in cotton and soybean plots than in corn and peanut plots from August through December.     

Effects of Subsoiling and Nematicides on Hoplolaimus columbus Populations and Cotton Yield

Subsoiling to a depth of 35 cm under the planting row for 3 consecutive years increased annual yields of seed cotton by 50 to 200%. Annual subsoiling was essential for maximum yields. The application of a nematicide, 1,2-dibromo-3-chloropropane (DBCP) or aldicarb, reduced the population of Hoplolaimus columbus but did not increase seed-cotton yields over subsoiling alone. Subsoiling reduced H. columbus in the top 20 cm of soil since the treatment favored deeper penetration by much of the root syslem and, consequently, less root colonization of the upper soil zone.     

Relative Tolerance of Selected Soybean Cultivars to Hoplolaimus columbus and Possible Effects of Soil Temperature

Eleven soybean [Glycine max (L.) Merr.] cultivars resistant to one or more plant-parasitic nematodes, and one resistant to the Mexican bean beetle (Epilachna varivestis Muls.), were tested for susceptibility to Hoplolaimus columbus. All cultivars were parasitized, but nematode reproduction varied. ''Pickett-71'' was the most susceptible host among the cultivars tested. ''Dyer'' and three ''P.I. cultivars'' were most tolerant when yield /plant and total yield were compared for fumigated and unfumigated plots, even though their yield potential was low. ''Hardee,'' ''Coker 4504,'' ''W-4,'' ''D71-9257,'' and ''ED-371'' appeared tolerant throughout the growing season and yielded well in unfumigated soil. Infection and reproduction of H. columbus in ''Forrest'' soybean roots were greater at 30 ± 1 C than at 20 or 25 ± 1 C. Plant height and root weight varied with the soil treatments.     

Tolerance to Heterodera glycines in Soybean

Fifty-four susceptible soybean, Glycine max, cultivars or plant introductions were evaluated for tolerance to H. glycines, the soybean cyst nematode (SCN). Seed yields of genotypes were compared in nematicide-treated (1,2-dibromo-3-chloropropane, 58 kg a.i./ha) and nontreated plots at two SCN-infested locations over 3 years. Distinct and consistent levels of tolerance to SCN were observed among soybean genotypes. PI 97100, an introduction from Korea, exhibited the highest level of tolerance with an average tolerance index ([yield in nontreated plot ÷ yield in nematicide-treated plot] × 100) of 96 over 2 years. Coker 156 and Wright had moderate levels of tolerance (range in index values 68 to 95) compared to the intolerant cuhivars Bragg and Coker 237 (range in index values 33 to 68). Most of the soybean genotypes evaluated were intolerant to SCN. The rankings of five genotypes for tolerance to SCN and Hoplolaimus columbus were similar. Tolerance for seed yield was more consistently correlated with tolerance for plant height (r = 0.55 to 0.64) than for seed weight (r = 0.23 to 0.65) among genotypes.     

Characterization of Heterodera sojae Virulence Phenotypes in Korea

The white soybean cyst nematode Heterodera sojae, isolated from the roots of soybean in Korea, is widespread in most provinces of the country and has the potential to be as harmful to soybean as H. glycines. Determining the virulence phenotypes of H. sojae is essential to devising management strategies that use resistant cultivars. Consequently, virulence phenotypes of 15 H. sojae populations from Korea were determined on seven soybean lines and one susceptible check variety. Two different HS types were found to be present in Korea; the more common HS type 2.5.7, comprising 73.3% of the H. sojae populations and the less common HS type 0, constituting only 26.7% of the tested populations. Considering the high frequency of H. sojae adaptation to soybean indicator lines, the PI 88788 group may not be a possible source of resistance while PI 548402, PI 90763, PI 437654, and PI 89772 can be used as resistance sources for soybean breeding programs aimed at developing H. sojae-resistant soybean cultivars in Korea.     

Rotylenchulus reniformis Management in Cotton with Crop Rotation

One-year crop rotations with corn or highly resistant soybean were evaluated at four locations for their effect on Rotylenchulus reniformis population levels and yield of a subsequent cotton crop. Four nematicide (aldicarb) regimes were included at two of the locations, and rotation with reniform-susceptible soybean was included at the other two locations. One-year rotations to corn or resistant soybean resulted in lower R. reniformis population levels (P ≤ 0.05) than those found in cotton at three test sites. However, the effect of rotation on nematode populations was undetectable by mid-season when cotton was grown the following year. Cotton yield following a one-year rotation to resistant soybean increased at all test locations compared to continuous cotton, and yield following corn increased at three locations. The optimum application rate for aldicarb in this study was 0.84 kg a.i./ha in furrow. Side-dress applications of aldicarb resulted in yield increases that were insufficient to cover the cost of application in 3 of the 4 years.     

Interactions of Concomitant Species of Nematodes and Fusarium oxysporum f. sp. vasinfectum on Cotton

Meloidogyne incognita, Hoplolaintus galeatus, and North Carolina and Georgia populations of Belonolaimus longicaudatus were introduced singly and in various combinations with Fusarium oxysporum f. sp. vasinfectum on wilt-susceptible ''Rowden'' cotton. Of all the nematodes, the combination of the N. C. population of B. longicaudatus with Fusarium promoted greatest wilt development. H. galeatus had no effect on wilt. With Fusarium plus M. incognito or B. longicaudatus, high nematode levels promoted greater wilt than low levels. The combination of either population of B. longicaudatus with M. incognita and Fusarium induced greater wilt development than comparable inoculum densities of either nematode alone or where H. galeatus was substituted for either of these nematodes. Nematode reproduction was inversely related to wilt development. Without Fusarium, however, the high inoculum level resulted in greater reproduction of all nematode species on cotton. Combining M. incognita with B. longicaudatus or H. galeatus gave mutually depressive effects on final nematode populations. The interactions of H. gateatus with B. longicaudatus varied with two populations of the latter.